Method of making negatives for line reproduction



B. RUDNICK Aug. 2s, 1945. A

METHOD OF MAKING NEGATIVES FOR LINE REPRODUCTION original Filed May 21, 1.941

w WM.. www W4 ATTORNE Y Patented Aug. 28, -1945 METHOD F MAKING NEGATIVES FOR LINE REPRODUCTION Benjamin'ltudnick, Huntington, N.- Y., assigner to Republic Aviation Corporation, a corporation oi.' Delaware Original application May 21, 1941, Serial No. 394,403. Divided and this application February 13, 1943, Serial No. 475,787 i 1 1 Claims.

This invention relates to a method of making negatives for line reproduction by which inscriptions, designs, or other graphic characters or delineations may be transferred from one surface to anotherv quickly, accurately and repeatedly, and isa division of application, Serial No. 394,403, led May 21, 1941, which matured into Patent Number 2,321,249 on June 8, 1943.

The present invention contemplates the creation of a permanent negative capable of receiving clear, sharp and distinct delineations or inscriptions, such for example as line drawings, which may be employed for the repeated reproduction of such inscriptions or delineatons upon a photographically light-sensitive positive.

The instant invention resides essentially in the application ofan opaque mask to a transparent base sheet which mask lis removed as a result of the delineation of a design on the negative to expose the transparent base thereby creating a negative having clear or transparent lines surrounded by an opaque iield.

Among its other objects the present invention has in view a complete line-for-line reproduction 4from the negative resulting from the present method, the lines of the reproduction being exact replicas of the lines in the negative, and the elimination of all roughness and irregularities in lthe line, as well as any diffusion resulting from refraction of the light employed in contact printing which diil'uslon of light would reproduce a widened or irregular line.

Other objects and advantages will be apparent from the following detailed description of the preferred mode of carrying out the method of my invention, reference being had to the annexed drawing in which:

Figure 1 is a cross-sectional View of a negative' prepared according to the preferredmethod;

Figure 2 shows the preferred manner in which.

complished by using said negative in the lightv contact printing, a printing method well known in the photographic arts long prior to this invention. The instant invention is concerned only with the creation of a ynegative which, when it has received the delineation of a drawing or dcsign, becomes the equivalent of the standard photographic negative commonly employed in contact printing. However, for the reproduction of mechanical layouts or drawings where the layout or drawing is made directly upon the negative it has been found that the negative must have certain c'haracteristics in order to meet the requirements of extremely accurate, clean, clear and precise reproduction, to-wit: it must be dimensionally stable; it must, in receiving the delineation of a design or drawing to be reproduced, create a transparent line of uniform width or thickness, clear cut and having no irregularities or variations therein, it must constitute and be able to comprise a permanent record capable oi repeated handling and reproduction. as well as storage without deteriorating or becoming damaged; and it must be capable of receiving and accepting corrections, changes and alterations in the design or drawing originally delineated thereon or be susceptible of correction and alteration during the delineation of a design or drawing thereon.

The end result of this method comprises a negative C having a transparent base or backing sheet 9. This sheet 9 may be glass or'any adaptable synthetic resin plastic or equivalent material havingdimensional stability and the capacity of freely transmitting light rays. One face of the backing sheet is completely covered by an opaque mask totally and completely impervious to the passage or transmission of light rays. This mask comprises the substantially individual coatings or layers l0 and Il. The coating Ill situated next to the backing sheet 9 is completely opaque and hence prevents the passage of light through the backing sheet 9. 'I'his opaque layer or coating I0 can be readily and cleanly fractured or removed from the backing sheet 9 and is held in place and protected from removal, disflgurement,y or fracture by the overlying binding layer Il which may be clearor pigmented. A

These layers I0 and Il combine to create a mask for the transparent backing sheet 9,the opacity of which results primarily from the characteristics of the maskingl coating I0 but may bev vsupplemented by the opacity, if any, 0f the bindthe desired'consistency. The percentage of the" lacquer vehicle to the quantity of the pulverulent pigment, such as aluminum, in the opaque layer I is very small, only enough lacquer or vehicle being employed to lightly adhere the minute grains of the pigment one to the other and the whole film to the surfacevof the backing sheet 9. To this extent the opaque coating I0 .may be said to 'have very little cohesion and adhesion and therefore is'unstable or frangible. v

If the coating or film I0 were unprotected, handling would disturb and dislodge portions or all of the nlm or coating and it would disintegrate. Therefore, the binding coating or layer Il is provided and functions to provide a binder and shield for the coating I0,.'an easily scribed vehicle to receive and record the delineations of drawings or designs, a surface capable of receiving and retaining pencil marks, and when desired, a surface not incompatible to light sensitive photographic emulsions and the adherence thereoughly before the coating Il is applied, and the coating I i being allowed to thoroughly dry before any delineation of drawings or designs on and through it. f

'I'he manipulation of the earlier steps in the a complete opaque mask on the one surface of of to the surface. In this layer li the same vepurpose of creating a contrasting color for the observation of lines delineated upon and through its surface and to overcome any glare or reection from the masking coating I0. Aside from accomplishing'these purposes the binding and shielding coating Il may be perfectly clear. Since this shielding and binding coating Il must be fractured or grooved and since its outer surface must readily receive pencil markings, and as it must resistwear, tear 'and manipulation and Ain so doing protect the underlying opaque coating lli, it must have certain strength and yet be fracturable evenly and uniformly without leaving ragged edges. A pigment is hence included in the vehicle butin this coating il the percentage of the vehicle or lacquer to the quantity of the pigl ment is far greater than the percentage of the vehicle or lacquer to the aluminum powder or pigment in the opaque coating I0.. This results in a far stronger coating having the required surface as above pointed out and more securely and permanently adhered to the underlying coating i0 and the backing sheet 9. The vehicle of the coating Il may be pigmented by material which will overcome the reflection from the aluminum of the coating I0, such as ilnely powdered tin or any other suitable pigment. It is desirable that the pigment employed in the shielding and binding coating Il be finely pulverulent so that this coating will fracture or groove cleanly and precisely when a drawing or design is delineated by scribing through it, the removed minute particles of pigment .bodily separating from each otherand from the mass of the coating along a sharp line, as the scribing operation does not tear the coating Il or disturb it at any point beyond the limits of the scribed mark. The resulting -coating Il has a color which destroys the glare or otherwise applied to the transparent backing sheet 9, the coating l0 being allowed to dry thorthe backing sheet 8. While any -method of application may be employed, it has been/found that these coatings ill and il may be successively applied to the backing sheet 9 with the usual spray gun. As the percentage of vehicle in the opaque coating l0 is relatively. small, there is substantially no cohesion between the` particles of the undercoating i0 and very little adhesion of the nlm or undercoating Il l as a whole to the backing sheet 9. In short, there is only sumclent adhesion between the film I0 and the backing sheet 9 to hold the former intact upon the latter until the binding coating I'I is applied thereto and dried. The application of a vehicle carrying the.pulverulent grains or minute particles to the sheet 9 to create the opaque undercoating |0- probably causes the minuteparticles contained in the lacquer vehicle to slightly overlap and to build up the opaque film. .Of course the particles themselves are opaque and therefore a multiplicity of overlying particles increases the opacity or makes assurance doubly assured that the opacity of the layer I0 .is complete and unbroken. When the opaque coating I0 is thoroughly dried, the binding coating Il is applied thereto. 'Ihe vehicle of the binding coating Il is of the same character as the vehicle that is employed in the underlying opaquecoating I0, and will penetrate or coact with the underlying coating I0 to increase its original inherent cohesion and adhesion as above noted.

To delineate a designor drawing on the negative sheet prepared as aforesaid, a metallic stylus with the groove or grooves created by the scribing aforesaid by brushing or erasing the particles of said coating I0 thereby uncovering or revealing the transparent-backing sheet 9 in registration or alignment withthegroove or grooves in the binding coating Il.

Since the opaque coating I0 principally consists of a multitude of small fragments or dust particles of aluminum or other opaque material or pigment, this coating partakes of the color of the aluminum particles or other opaque pigment employed in the coating, and this color usually presents an unsatisfactory drawing surface and gives very poor contrast .to pencil marks or to the transparent parts of the backing sheet 9 exposed by the scribing of the mask iii-I I. Hence pigment is incorporated with the binding coating I I,

which would otherwise require no-pigmentation.

The nature of the pigment in the binding coating Il is such that the removal thereof by the scribing operation will in result and principle be like the removal of the opaque coating I0.

'I'he removal of this coating Il' in correspondence with the groove or grooves formed in the outer binding coating Il because of the unstable nature thereof is accomplished byl a brush or eraser whereby only those particles of'opaque pigment in alignment with the groove or grooves in the outer binding coating Il are removed, leaving the remaining particles undisturbed.

A The scribing operation or step removing the outer coating il does so evenly and smoothly so that the coating Il remaining a part of the negative is not broken, checked or disturbed. Thus the line to be reproduced is created clearly andv sharply inthe form of a groove in each layer l0 and Il which'grooves are in exact registration and of the same width throughout.

As the binding coating i I is easily fractured by the scriber, the force employed in so fracturing it is not suiiicient to appreciably break `or go through the opaque inner coating I0. Hence thev surface of the transparent sheet 9 is fully and I completely protected` from contact withv the scriber which might scratch or groove the surface of the sheets to some Adegree if contact were established during the scribing operation. If that occurred. light passing through the negative from the coated side thereof would strike the .chamber causing the emuniop to Jeu, after which it is placed in a dryer.

The prepared positive B may be used as soon as it is dry, or it maybe stored'away in a light-tight cabinet for future use. In transferring the drawing from the negatively prepared surface (as will be described in detail hereinafter) of a nega'- tive sheet C (Figure 1) to the positively prepared surface of the positive B, the pattern sheet is placed upon a flat, solid support in a dark room, treated face up, and the positive is superimposed upon the pattern sheet with its treated face held firmly in engagement with the treated face of 4the negative to i sure absolute. contact therebetween. Under suc conditions, the light rays emitted during the exposure' act photographically upon the light-sensitive emulsion and cause the silver salts to be suiiiciently affected usually inv about one and one-half to two minutes. The thus-exposed positive B, is finally removed and treated with the usual developing and fixing solutions in a manner which is well-known scratch in the transparent' sheet 9 and would n thereby be retracted to create diffusion' and a widened irregular line in the print made from the negative. This would not. however. occur when the light passed through the negative from the uncoated side because the light rays before reaching the positive would, in that event, be sharply confined by the registering grooves in the coatings lil-II but since the negative is used for reproduction purposes .with the light for contact printing passing through it from either )side it is as a filler for closing the pores of the material composing the backing sheet, and as a protective shield between the backing sheet and the emulsionwhich is subsequently applied thereto, and which otherwise might interact chemically With the backing material. I preferv to'use as the primer a suspension of zinc chromate in a carrier selected with consideration to the-nature of the material composing the positive. When the positive is composed of a metal such as steel, both of` its faces, as well as its edges, will be covered with v the primer to avoid contamination of the chemicals employed in the subsequent eration.

The positive is next' placed in a dark room illuminated, for example, by a ruby safelight of the time Well known to photography; the temperature is maintained substantially constant and an emulsion -8, consisting, for example .of a light-sensitive material, such as silver nitrate suspended in a gelatinous vehicle, is melted and applied as a film inany suitable manner giving an even thickness, though I prefer to apply it with a low-pressure spray gun smoothly yand uniformly over the primer coating. The thus-prepared sheet is then passed through a chilling developing opto the photographic art, and then washed and dried. Because the negative surface is not affected by said exposure, a great number of copies written and printed indicia, maps, charts, me-

chanical layouts, etc.

. Manifestly Vvarious other modifications in the foregoing method may be made by those skilled in the art without departing from the spirit of my invention as defined in thefollowing claims.

I. claim:

The method of making a negative for line reproduction consisting of providing a transparent backing sheet with an opaque, frangible undercoat, applying an outer coat thereto, delineating a design to be reproduced by scribing the lines representing the design in the form of grooves extending throughsaid outer coat. and removing those portions of the undercoat in alignment with the aforesaid grooves thereby exposing corresponding portions of the transparent backing sheet.

2. The method of making a negative for line reproduction consisting in providing atransparent, backingsheet with an opaque, frangible coat relatively non-cohesive and only slightly adhesive to the backing plate, applying an outer coat of protecting and binding material to said undercoat, delineating a design to be reproduced in the form of grooves scribed through the outer coat, and removing those portions of the undercoat in direct alignment with said grooves, thereby exposing corresponding portions of the transparent 'backing sheet and leaving the remainder of the outer coatings and exposing portions of the backf ing sheet corresponding to said grooves.

4. The method of making a negative for line reproduction consisting in lightly adhering a rel.

4 asaaso? atively unstable, opaque undercoating to a transparent backing sheet, applying a relatively stable outer coating completely over said undercoating, scriblng grooves through the outer coating, and removing those portions of the undercoating in alignment with. said grooves, thereby exposing the corresponding portions of the backing sheet.

5. The method of making a negative for line reproduction consisting in depositing a frangible, opaque masking layer comprising a finely powdered aluminum and a relatively small quantity of lacquer on a transparent backing sheet, covering said masking layer witha binding layer comprising a relatively large quantity of lacquer. and removing both of said layers in correspondence with the lines to be reproduced to exposed aligned portions of the backing sheet.

6. The method of making a, negative for line reproduction consisting in depositing amasking layer comprising opaque particles and lacquer on a transparent backing sheet, covering said masking layer with a binding layer comprising lacquer and a pigment, the ratio of lacquer tc opaque particles in the masking layer being less than the ratio of lacquer to pigment in the binding layer, and removing, the both layers in correspondence to the design to be reproduced to expose aligned portions of the backing sheet.

7. Thel method of making a negative for line reproduction consisting in depositing a masking c layer composed principally of opaque particles 8. The method of making a photo-mechanical negative consisting in compounding finely powdered opaque material with a relatively small quantity of lacquer dissolved in a volatile solvent and diluted to spraying consistency, spraying the resulting compound on one surface o! a transparent backing sheet to deposit an opaque masking layer mainly comprising the powdered opaque material lightly adhered to said sheet, and covering said masking layer when dry with a lacquer binding layer.

9. The method of making a photo-mechanical negative consisting in compounding tlnely powdered metal with a relatively small quantity of nitrocellulose, depositing this compound on one surface of a transparent sheet in a comparatively thin masking layer mainly comprising powdered metal lightly adhered to said sheet, depositing a binding layer of nitrocellulose on said masking layer, and delineating a design to be reproduced in the form of grooves extending through both layers to expose the underlying transparent sheet.

10.- 'I'he methodof making a photo-mechanical negative consisting in compounding inely powdered aluminum with a relatively small quantity of nitrocellulose dissolved in a volatile solvent and diluted to spraying consistency, spraying the resulting compound upon one surface of a transparent backing sheet t9 deposit the powdered aluminum in a relatively thin opaque masking layer lightly adhered to said sheet, andspraying said masking layer when drywith a mixture of nitrocellulose and a volatile solvent diluted to spraying consistency to create a binding layer covering and protecting the masking layer aforesaid.

1l. The method of making a photo-mechanical negative for line reproduction consisting in compounding flnely powdered aluminum with a relatively small quantity of lacquer comprising nitrocellulose and solvents diluted 'to spraying consistency, spraying the resulting compound on one surface of a transparent backing sheet to deposit a relatively thin, opaque, iriable masking layer of aluminum, covering said masking layer of aluminum on said sheet with a binding layer by spraying it with a lacquer comprising nitrocellu-V lose and solvent diluted to spraying consistency.

- and scribing the lines to be reproduced through both of said layers to expose corresponding portions of the backing sheet.

BENJAMIN RUDNICK. 

